Injection product for sealing and/or consolidating soils and building materials, and a method for its employment

ABSTRACT

Impermeabilization and/or consolidation product for soils and building materials, usable by injection, characterized by the fact that it is obtained by mixture of a compound of slag in suspension in water and of a silica liquor having a ratio of SiO 2  Na 2  O lower than 2 and a silica content greater than about 10% by weight.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to an injection product for theimpermeabilization and/or consolidation of soils and building materials,such as mortars, binders, masonry, concretes etc., having more or lessdeep fissures or voids that might result in porosity and hencepermeability.

The present invention relates also to a method of employing such aninjection product for the purpose of improving the impermeability ofand/or of consolidating such soils and building materials.

More particularly, the present invention is intended for the treatmentof particularly fine or very fine materials and soils to modify theirconsistency.

For the sealing and/or consolidation of soils and materials it iscurrent practice to use cement-base sealing and/or consolidatingproducts still called "grouts" when the pores are more or less large, orsilica gel type products obtained by jelling sodium silicate, when thepores are particularly fine.

This latter class of grouts, however, may cause the problem of pollutingthe soil, particularly at the level of the water tables, and also ofpoor durability since the structure of the gels obtained may not belastingly stable. This phenomenon, known as "syneresis," can be veryharmful to the gels obtained from silicate solutions.

To remedy the deficiencies of these injection grouts French patentNo.83.09647 has proposed an injection grout particularly for microporesand microfissures, which is in the form of a noncolloidal silica liquorobtained by dissolving at ambient temperature silica having an averageparticle diameter less than 100 microns in soda, the ratio of SiO₂ toNa₂ O being less than 2 and the silica content of the solution beingpreferably greater than about 20% by weight.

This type of grout is highly reactive to calcium, which is present inbuilding materials and certain soils, and therefore leads to amineralization of soils and/or building materials by the formation ofstable and insoluble hydrated calcium silicates, thus assuring thepermanence of the treatment performed on these soils and materials.

These grouts present certain problems, however, due to the fact that thesetting time has proven to be particularly sensitive to temperatureconditions and to the concentrations of the various products present.

In certain applications it is particularly important to have grouts thathave a constant and controllable setting time.

When the point of injection is remote from the place where the grout isprepared it is important to have grouts which have a variable butconstant setting time, so as to assure good repeatability of theinjection operations.

In French Patent No. 72.06150 it has been proposed, in order to vary thesetting time, to replace a portion of the cement of an injection groutcontaining sodium silicate or an aqueous solution of sodium silicate anda cement paste, with a mineral substance having latent hydraulicproperties, such as a finely granulated slag.

Although the addition of slag actually does affect the setting time, itis too fast, even with heavy concentrations of slag. Furthermore, thistype of sodium silicate base grout already has, at time t=0, a highviscosity (>15 cp) which does not allow it to be injected into very finesoils such as Fontainebleau sands.

The present invention permits the solution of the problems involved inknown grouts and therefore it proposes a sealing and/or consolidationproduct for soils and building materials having a stable andcontrollable setting time and having furthermore an appropriateviscosity to permit good penetration into fine or very fine soils aswell as in the fissures and microfissures in building materials.

Quite surprisingly and unexpectedly, it has been found that, inaccordance with the invention, the addition of slag to the grout inaccordance with French patent No. 83.09647 resulted in setting times oflonger than about 1 hour, whereas the grout according to French patentNo. 72.06150 had a setting time of several minutes or, in any case, lessthan one hour.

Such a difference in reactivity was quite unforeseeable inasmuch as itis well known that grouts based on silica liquor have a much greaterreactivity than grouts based on sodium silicate.

DETAILED DESCRIPTION OF THE INVENTION

The sealing and/or consolidating product according to the invention haspreferably a viscosity at t=0 of generally between 4 and 6 centipoises(cp).

The slag compound should be preferably of the basic type and have aratio of CaO:SiO₂ between 1.10 and 1.35.

According to the invention a blast furnace slag is preferably used whichhas the following chemical composition by weight:

SiO₂ =33 to 40%

Al₂ O₃ =8 to 16%

CaO=40 to 45%

the balance consisting of MgO, Fe₂ O₃, K₂ O, Na₂ O, S--, MnO, TiO₂ andother traces of minor elements.

The granulometry of the slag is of some importance in that the averagediameter of the particles should be smaller than the pores andmicrofissures that are to be injected with the grout.

In practice, the diameter of the slag particles is generally between 0and 120 microns, which corresponds to a Blaine specific surface area of3,000 to 4,000 cm² /g.

For the injection of particularly fine pores and microfissures the slagcan be in the form of very fine particles having a Blaine specificsurface area of about 10,000 cm² /g.

Also usable as a slag compound according to the invention is a slag-basecement in which the slag percentage is greater than 60% by weight,particularly cements of type CLK 45, which are clinker slag cementscontaining more than 80% by weight of slag.

The silica liquor which is added to the slag has the effect ofcatalyzing the setting and curing reactions.

This liquor is obtained by dissolving, at ambient temperature, silica ofan average particle diameter of preferably less than 100 microns insoda, the SiO₂ :Na₂ O ratio being, as indicated above, less than 2 butpreferably between 1.5 and 1.8.

The silica used can be silica in the pure state or, preferably,siliceous products containing at least 80 to 90% by weight of SiO₂ of anonvitreous structure.

Particularly to be mentioned among the preferred compounds are thepyrogenic silicas also called smoky silicas originating from industrialwastes, kieselguhr, gaize, or also silica aerogels.

The granulometry of the silica for obtaining quick and completedissolution in the soda must be under 100 microns, and preferably under50 microns.

The soda used for dissolving the silica is preferably in the form of asolution of between 35° and 37° B, i.e., one having a density betweenabout 1.32 and 1.35.

The amount of silica liquor can be variable, but it is generally between20 and 80 liters per 100 kg of the slag compound.

The studies that have been made have shown that the greater the amountof silica liquor was with respect to the slag compound, the faster wasthe setting time.

The setting time of one hour was observed for a grout containing 45liters of silica liquor per 100 kg of blast furnace slag, and a settingtime of about 2 hours for a grout containing 35 liters of silica liquorper 100 kg of slag.

The amount of water in the grout according to the invention, for thesuspension of the particles of the slag compound, will depend on thestrength and on the viscosity that it is desired to obtain.

This amount of water is generally between 200 and 1000 liters, andpreferably between 500 and 800 liters, per 100 kg of the slag compound.

According to a preferred embodiment of the invention, the grout can alsocontain calcium carbonate powder which can be made by crushing marble,limestone or calcite.

This charge of calcium carbonate is particularly recommended for thetreatment of certain soils and/or materials of low lime content.

According to this embodiment, the silica liquor reacts with the Ca⁺⁺ions which are released progressively by hydrolysis to form insolubleand stable hydrated calcium silicates.

The presence of calcium carbonate powder moreover makes it possible toregulate the viscosity and the strength of the grout. If necessary, itis also possible to add quicklime or slaked lime to regulate the curingtime.

In fact, for certain applications, it is particularly important to makethe curing time as short as possible, particularly in fast-drainingsoils.

The present invention also has as its subject matter a process ofsealing and/or consolidation, this process consisting of injecting underpressure the grout in accord with the invention, as defined above, intothe pores or microfissures of soils or building materials by means ofconventional injection apparatus. The process according to the inventionis quite particularly intended for the treatment of ground that is to beimpermeabilized or to be consolidated, whether it be fissured rock oralluvial soils.

The injection pressure is generally between 5 and 20 bar and the amountof grout between 2 and 40% of the volume of the ground that is to betreated.

When impermeabilization is being performed, the treatment can bemonitored by taking a sample and subjecting it to permeabilitymeasurements.

For the purpose of aiding in the comprehension of the invention, anumber of examples of the making and employment of the grout inaccordance with the invention will now be described by way ofillustration, without in any way limiting the invention thereto.

EXAMPLE 1

For the purpose of impermeabilizing a fine sand by injection, first ofall a suspension is prepared of 145 kg of blast furnace slag (CaO:SiO₂=1.20) having an average particle diameter of 10 microns in 1,000 litersof water. To this suspension are added 90 kg of slaked lime and 60liters of silica liquor obtained in the following manner:

170 kg of silica of an average grain size of about 50 microns isdissolved in 300 liters of soda of 36° B and 70 liters of water. Aslight exothermic reaction is noted during dissolution (thecharacteristics of the solution after formation were the following:ratio SiO₂ :Na₂ O=1.8%, SiO₂ =26.6%; Na₂ O=14.8%; H₂ O=58.6%; viscosity40-50 cp).

The grout thus obtained has a viscosity (t=0) of 5 cp and a setting timeof 1 h30, and a curing time of 4 hours.

This grout is then pressure-injected by conventional techniques throughan injection tube introduced by drilling. When the back pressure becamesteady at about 10 bar the injection was stopped. A permeability testshows a perfect impermeabilization of the ground thus treated.

EXAMPLE 2

The precedure was as in Example 1, but with a quantity of 100 liters ofsilica liquor. In this case it was found that the setting time was 1hour and the curing time 4 hours.

EXAMPLE 3

The procedure was as in Example 1, but using a grout obtained bysuspending 300 kg of blast furnace slag in 1,000 liters of water andadding 180 liters of the same silica liquor.

EXAMPLE 4

The procedure was as in Example 1, but using a grout obtained bysuspending 150 kg of CLK 45 cement in 1,000 liters of water and adding100 liters of the same silica liquor. The setting time of this grout was1 hour.

I claim:
 1. An improved injection product for impermeabilization and/orconsolidation of soils and building materials, comprising a mixtureof:(a) a compound of slag in suspension in water; and (b) a silicaliquor which is dissolved silica having an average particle diameterless than 100 microns in soda; having a ratio of SiO₂ /Na₂ O less than 2and a silica content greater than about 10% by weight.
 2. An injectionproduct according to claim 1, characterized by the fact that:(a) theslag compound has a CaO:SiO₂ ratio between 1.10 and 1.35.
 3. Aninjection product according to claim 1, characterized by the factthat:(a) the slag compound is blast furnace slag which has a particlediameter less than 120 microns.
 4. An injection product according toclaim 1, characterized by the fact that:(a) the slag compound is CLKcement containing more than 80% by weight of blast furnace slag.
 5. Aninjection product according to claim 1, characterized by the factthat:the SiO₂ :Na₂ O ratio is between 1.5 and 1.8.
 6. An injectionproduct according to claim 1, characterized by the fact that:(a) theamount of silica liquor per 100 kg of slag compound is between 20 and 80liters.
 7. An injection product according to claim 1, characterized bythe fact that:(a) the amount of water for the suspension of the slagcompound is between 200 and 1,000 liters per 100 kg of the slagcompound.
 8. An injection product according to claim 1, characterized bythe fact that:(a) the product further contains calcium carbonate power.9. A method for the impermeabilization and/or consolidation of soils andbuilding material, including the step of injection under pressure of amixture of a compound of slag in suspension in water and a silica liquorwhich is dissolved silica having an average particle diameter less than100 microns in soda; having a ratio of SiO₂ /Na₂ O less than 2 and asilica content greater than about 10% by weight.
 10. The method of claim9 further characterized in that the injection pressure is 5-20 bar andthe volume of the injected mixture is 2-40 percent of the volume ofmaterial being treated.